Conference Paper

Octopus-inspired Eight-arm Robotic Swimming by Sculling Movements

DOI: 10.1109/ICRA.2013.6631314 Conference: IEEE Int. Conf. Rob. Autom. (ICRA'13), Volume: pp. 5135-5141


Inspired by the octopus arm morphology and exploiting recordings of swimming octopus, we investigate the propulsive capabilities of an 8-arm robotic system under various swimming gaits, including arm sculling and arm undulations, for the generation of forward propulsion. A dynamical model of the robotic system, that considers fluid drag contributions accurately evaluated by CFD methods, was used to study the effects of various kinematic parameters on propulsion. Exper- iments inside a water tank with an 8-arm robotic prototype successfully demonstrated the sculling-only gaits, attaining a maximum speed of approximately 0.2 body lengths per second. Similar trends were observed, as in the simulation studies, with respect to the effect of the kinematic parameters on propulsion.

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    • "The temporal variation of the angular velocity xðtÞ and the angle of rotation /ðtÞ may take various forms for a two-stroke motion profile, in which the arm rotates upwards and downwards in a cyclic way. Here, we examine two basic profiles, as displayed in Fig. 2a and b: a sinusoidal oscillation, and a sculling profile [4] [5] [37] [38] of different velocity ratio b between a relatively slow upstroke (termed as recovery stroke [37]) and a considerably faster downstroke (termed power stroke [37]). These motion profiles originate from observations of live octopus and analysis of the reconstructed 3D arm trajectories, during arm-swimming motion, in the way described in the previous paragraph and presented in Fig. 1. "
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    ABSTRACT: The complexity in structure and locomotion of cephalopods, such as the octopus, poses difficulties in modeling and simulation. Their slender arms, being highly agile and dexterous, often involve intense deformations, which are hard to simulate accurately, while simultaneously ensuring numerical stability and low diffusion of the transient motion results. Within the immersed-boundary framework, this paper focuses on an arm geometry performing prescribed motions that reflect octopus locomotion. The method is compared with a finite-volume numerical approach to determine the mesh requirements that must be employed for sufficiently capturing, not only the near wall viscous flow, but also the off-body vortical flow field in intense forced motions. The objective is to demonstrate and exploit the generality of the immersed boundary approach to complex numerical simulations of deforming geometries. Incorporation of arm deformation was found to increase the output thrust of a single-arm system. It was further found that sculling motion combined with arm undulations provides an effective propulsive scheme for an octopus-like arm.
    Full-text · Article · Jul 2015 · Computers & Fluids
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    • "Although this captures the basic motion components, a more quantified kinematic description would reveal new aspects of this unique propulsion mode if implemented in robotic models. We have recently presented a multi-arm underwater robot [11]–[14] that mimics the morphology of the octopus, possessing 8 compliant arms and a passively-compliant web. The robotic model has included detailed information of hydrodynamic results [15]–[18] and is in accordance with relevant elastodynamic investigations of arm muscle activation [19], [20]. "
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    ABSTRACT: The octopus uses the arm-swimming behavior primarily for escape, defense, or foraging. This mode of locomotion is comprised of two strokes, with the arms opening slowly and closing rapidly, and generally results in considerable propulsive acceleration. In light of the recent development by our group of an octopus-like eight-arm underwater robot, we are interested to analyze the details of the biological arm swimming motion, in order to understand its kinematics. In this paper, we address methodological aspects of the 3D reconstruction process of octopus arm trajectories, based on computer vision, and present the resulting arm swimming movement of a benthic common octopus. The 3D trajectories of all eight octopus arms were tracked and analyzed, providing information about speed, acceleration and arm elongation. The animal's performance is then used for a direct comparison with our 8-arm robotic swimmer. The data obtained provide new kinematic information about this, relatively unknown, propulsive mode, which can be exploited for multi-functional underwater robots.
    Full-text · Article · Jun 2015 · Proceedings - IEEE International Conference on Robotics and Automation
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    • "Cephalopods, such as squids and octopuses, often propel themselves in water by resorting to a sequence of cyclic contractions and expansions of a soft cavity of their body, commonly referred to as the mantle [1]. While squid may rely on fin-assisted swimming [2] and octopuses are observed to use arm sculling [3], here we will be dealing exclusively with the pulsed-jet mode of propulsion. "
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    ABSTRACT: This paper entails the study of the pulsed-jet propulsion inspired by cephalopods in the frame of underwater bioinspired robotics. This propulsion routine involves a sequence of consecutive cycles of inflation and collapse of an elastic bladder, which, in the robotics artefact developed by the authors, is enabled by a cable-driven actuation of a deformable shell composed of rubber-like materials. In the present work an all-comprehensive formulation is derived by resorting to a coupled approach that comprises of a model of the structural dynamics of the cephalopod-like elastic bladder and a model of the pulsed-jet thrust production. The bladder, or mantle, is modelled by means of geometrically exact, axisymmetric, nonlinear shell theory, which yields an accurate estimation of the forces involved in driving the deformation of the structure in water. By coupling these results with those from a standard thrust model, the behaviour of the vehicle propelling itself in water is derived. The constitutive laws of the shell are also exploited as control laws with the scope of replicating the muscle activation routine observed in cephalopods. The model is employed to test various shapes, material properties and actuation routines of the mantle. The results are compared in terms of speed performance in order to identify suitable design guidelines. Altogether, the model is tested in more than 50 configurations, eventually providing useful insight for the development of more advanced vehicles and bringing evidence of its reliability in studying the dynamics of both man-made cephalopodinspired robots and live specimens.
    Full-text · Article · Jun 2015 · International Journal of Advanced Robotic Systems
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